ASSESSING THE GLOBAL AND ARCTIC TRANSPORT OF POLYCHLORINATED BIPHENYLS UNDER PRESENT AND FUTURE CLIMATE AND EMISSIONS

Abstract:

We simulate the present and potential future atmospheric transport and fate of polychlorinated biphenyls (PCBs), using the global chemical transport model GEOS-Chem. PCBs are toxic, persistent, and bioaccumulative chemicals whose production and use have been banned internationally. PCBs continue to cycle through the global atmosphere, however, because of their persistence, passive emissions from remaining stocks, and release from natural storage reservoirs such as oceans or soils. In particular, PCBs have been shown to transport long distances in the atmosphere to locations remote from emissions, such as the Arctic, where they can accumulate in wildlife and humans, putting health at risk. Previous studies have suggested that PCBs may be remobilized in a changing climate because higher temperatures will cause greater re-emissions from surface reservoirs. Here, we modify GEOS-Chem to simulate atmospheric PCB transport and investigate the relative effects of predicted climate changes and projected declines in primary emissions, especially on transport to the Arctic. We quantify changes in atmospheric concentrations of two PCBs (CB28 and CB 153) under 2050 climate (“FC”); 2050 emissions (“FE”); and 2050 climate and emissions combined (“FCFE”); relative to a 2000 climate, 2000 emissions control scenario, and determine the major processes affecting these changes. In the version of the model presented here, only soil-atmosphere surface interactions are considered, though future versions will include interaction with other surface media. Our results suggest projected 2050 emissions will play a stronger role than 2050 climate in controlling PCB concentrations of different volatilities. Temperature increases under FC cause increases in emissions of only 4% at most, resulting in negligible concentration changes relative to the FE scenario, in which primary emissions are projected to decline to <0.05% of present-day. Thus, the concentrations in the combined FCFE scenario are dominated by changes from the FE scenario. Likewise, changes in re-emissions are more strongly impacted by the substantial decline in atmospheric concentrations under FE than they are by temperature changes under FC.